Guide to Starting Annual Flower Seeds

Most annual flower seeds are easy to start indoors. And by starting your own bedding plants, you’ll not only save money, but you’ll also be able to grow hundreds of cultivars and unusual species not available at the garden center.

AgeratumAgeratum houstonianum

Butterflies love ageratum’s fuzzy blue, pink, or white blooms. Grow these mounding plants in beds or containers and be sure to cut some stems for indoor arrangements, too.

To start seeds indoors: Start the seeds 6 to 8 weeks before the last frost date. Scatter the seeds on the surface of the soil—don’t cover them because they need light to germinate. Keep the soil temperature at 70° to 80°F; sprouts should appear in 5 to 10 days. Transplant the seedlings outdoors after all danger of frost has passed.

Snapdragon flowers come in all major colors except blue, as well as in combinations of two and three hues. The long flower spikes of the upright cultivars are excellent for cutting gardens; dwarf cultivars make colorful groundcovers.

To start seeds indoors: Sow seeds of upright cultivars 6 to 8 weeks before the last frost date; start dwarf cultivars about 4 weeks before the last frost date. Scatter seeds on the surface of the medium, but don’t cover them—they need light to germinate. Keep the soil temperature at 70° to 75°F; sprouts should appear in 10 to 20 days. Transplant the seedlings outdoors after the last frost.

VincaCatharanthus roseus

These bushy 12-to 14-inch plants bear a profusion of single blooms in white, apricot, pink, or rose. ‘Stardust Orchid’ produces big blooms and is easy to grow.

To start seeds indoors: Start the seeds indoors about 8 to 10 weeks before your last frost date. Sprinkle seeds over the moist medium, cover them with a scant 1/6 inch of soil, then lay damp newspaper over the soil surface to keep the seeds moist and dark. Maintain the soil temperature at 70° to 75°F. Check daily for signs of germination; remove the paper as soon as sprouts appear (2 or 3 days). Plant the seedlings outdoors 2 to 4 weeks after your last frost date.

Whether you grow the “plumed” type, which looks like big feathers, or the “crested” type, curled like the combs of a rooster, celosia adds bold color to beds or containers. The stems are good for cutting, too.

To start seeds indoors: Sow seeds 4 to 6 weeks before the last frost date, barely covering them with medium. Keep the soil temperature at about 75°F. When seeds germinate (about 5 to 10 days), lower the temperature to 65° to 70°F. Feed 2-week-old seedlings with diluted fish emulsion and repeat 2 weeks later. Set out the seedlings 2 weeks after the last frost date; transplanting them sooner can hurt flowering later in the season.

Cosmos bears single white, pink, lavender, or burgundy blooms from summer through frost. Dwarf cultivars, such as ‘Sonata’, tend to bloom earlier than taller-growing types.

To start seeds indoors: About 4 to 6 weeks before the last frost date, sow the seeds, covering them with about 1/8 inch of medium. Keep the temperature at about 70°F. When seeds sprout (5 to 7 days), lower the heat to about 60°F and provide bright light to keep them from becoming “leggy.” Transplant seedlings outdoors around the last frost date.

The upright, branching plants of globe amaranth bear cloverlike red, purple, pink, and white blooms that are excellent for drying. Pick the flowers often to keep the blooms coming.

To start seeds indoors: Start seeds indoors 6 to 8 weeks before the last frost date. Barely cover the seeds with soil and keep the temperature at about 72°F. Germination should occur in 10 to 14 days. Transplant seedlings outdoors around the last frost date.

Popular sunflowers have finally made their way out of vegetable gardens and into flowerbeds, entryways, and even containers. Experiment with some of the newer cultivars that offer bicolored blooms, bushy shapes, and dwarf size.

To start seeds indoors: Sow seeds 4 to 6 weeks before the last frost date. Cover the seeds with ½ inch of soil and keep the temperature at 70° to 85°F. Seedlings will emerge in 5 to 14 days. Set out the plants after the last frost.

Arguably the best flower for shady areas, impatiens bloom nonstop from the time you transplant them to the garden until frost. The 6-to 30-inch tall plants cover themselves with single or double blooms in pink, red, purple, orange, salmon, and white—both solid shades and bicolors.

To start seeds indoors: Sprinkle the seeds on the surface of the premoistened starting medium, about 8 to 10 weeks before your last frost date. Don’t cover the seeds—they need light to germinate. Set the containers directly beneath fluorescent lights; keep the soil moist and at 70° to 80°F. Seeds should sprout in 1 to 3 weeks. Transplant the seedlings outside a week or two after the last frost date.

To start seeds indoors: Sow the seeds on the surface of the medium without covering them, about 6 to 8 weeks before the last frost date. Keep the soil temperature at 60° to 75°F. Germination should occur in 1 or 2 weeks. Transplant the seedlings outdoors around the last frost date.

Melampodium bears beautiful small, golden, daisylike blooms on bushy plants that tolerate heat, drought, and pests. Grow them as an edging plant or in containers.

To start seeds indoors: About 14 weeks before your last frost date, sprinkle the seeds over a premoistened medium, then cover the seeds lightly with vermiculite. Keep the temperature at 65° to 70°F. Sprouts should appear in a week or two. Transplant the seedlings to the garden 2 weeks after your last frost date.

Starting petunias from seed opens the door to a wide world of beautiful, tubular flowers in shades ranging from striking magenta to subdued lavender to pure white.

To start seeds indoors: Sprinkle seeds onto the surface of the premoistened medium, 10 to 12 weeks before the last expected frost. Don’t cover the seeds—they need light to germinate. Set the flat beneath lights and keep the soil temperature at 70° to 80°F. When seedlings appear (about 10 days), lower the temperature to about 60°F. Transplant seedlings outdoors around the last frost date.

Marigolds thrive in just about any climate. And although you can sow the seeds directly in your beds in spring, you’ll be able to enjoy their sunny yellow, orange, and bicolored flowers much earlier if you start the seeds indoors.

To start seeds indoors: Sow the seeds about 6 weeks before your last frost date, covering them with a very thin layer of soil. Keep the soil temperature at 70° to 75°F. Sprouts will appear in 5 to 7 days. Plant the seedlings outdoors anytime after the last frost.

Zinnias offer an assortment of bloom colors and shapes on plants that range from 1 to 4 feet tall. Many are great for cutting. If you garden in a humid area, try the newer mildew-resistant varieties, such as ‘Oklahoma’ or ‘Profusion’.

To start seeds indoors: Start Z. elegans cultivars 4 weeks before your last frost date; start slower-growing Z. angustifolia 6 to 8 weeks before that date. Sow the seeds in individual peat pots, barely covering them with soil. Maintain a temperature of 70° to 80°F until the seeds sprout—about a week. Then, lower the temperature to about 60°F. Transplant to the garden around the last frost date.